SGSN bug report

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Holger Hans Peter Freyther holger at freyther.de
Sat Oct 25 09:44:50 UTC 2014


On Sat, Oct 25, 2014 at 06:18:38PM +0900, Pierre Kim wrote:
> Hello,

Hi,

> I am using a nanoBTS EDGE model.

that is what I assumed. You will need to figure out what the
ip.access PCU is doing.

> An iPhone on the same BTS doesn't have this issue.
> But Samsung phones and HTC Diamond do.

Different stacks, different firmware, it doesn't say much. But
please have a look at the trace:

Packet	Delta-TS	Direction	TLLI		message
#7	0		MS->SGSN	2584537203	GMM Attach Request
#8	~0s		SGSN->MS	2584537203	GMM Identity Request
#10	~2s		PCU->SGSN	-		LLC Discarded

In packet #10 the PCU tells the SGSN that 9 octets could not be
transferred. Assuming you included the full trace the '9' are the
nine bytes of the "LLC/GMM Identity Request".

This means that the closed source PCU of the nanoBTS EDGE model
couldn't transfer the LLC data to the MS within the 2s deadline
that was set in the PDU-Lifetime of packet #8. Now nobody in this
community can tell you why the PCU of the nanoBTS doesn't transfer
it. Last time I tried to contact an engineer at ip.access (the one
that patched GSMTAP for PDCH handling), I was ignored.

kind regards
	holger





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